The present invention relates generally to magnetic data storage systems. More particularly, the present invention relates to a magnetic writer pole used in such systems.
Magnetic heads mounted on a magnetic disc drive are required to provide larger magnetic fields with higher gradient for magnetic recording at higher density. More recent magnetic heads combine both a magnetoresistive (MR) or giant magnetoresistive (GMR) element for reading information from a magnetic medium and an inductive element for writing information to such a magnetic medium. Such magnetic heads are typically referred to as composite thin film magnetic heads or merged GMR heads. The magnetic head is mounted or embedded in a slider which is supported in transducing relationship with respect to a magnetic medium.
The inductive write head element includes first and second poles which have first and second pole tips respectively. The pole tips are separated by a gap at an air bearing surface (ABS) or head surface. A coil is positioned between the first and second poles. Applying an electrical current to the coil results in a magnetic field being generated between the poles. The direction of the current through the coil determines the polarity of the induced magnetic field. The induced magnetic field causes magnetic particles in the adjacent magnetic medium to line up in one direction or the other, depending on the polarity of the induced magnetic field. In this way, information is written on the magnetic medium.
Flux density, which is a measure of the quantity of magnetism, needs to be high in the inductive head element for it to provide a high magnetic field for writing. There are limitations to the capability of the inductive head element to provide high flux density since materials have a saturation level beyond which they will conduct no more flux. Similarly, magnetic moment, which is a measure of the strength of the magnet, does not change beyond a certain level (reaches saturation) even if the strength of the applied magnetic field is increased. A high saturation magnetic moment is very desirable for write heads recording at high areal densities, the areal density being the amount of data that can be squeezed on to a given area of the magnetic medium. If the pole tip saturates, it loses its permeability, and will eventually act as an additional writer gap. Saturated pole tips result in increases in pulse width and bit curvature. Consequently, it becomes very difficult to write at high areal densities because of the poor resolution of the bit/transition. Further, finite element modeling or analysis of magnetic recording indicates that a high saturation magnetic moment is particularly critical for those magnetic layers adjacent to the non-magnetic gap layer of the write head.
The use of materials with high magnetic moment for writer pole tips allows for the generation of higher magnetic fields in the magnetic media, larger field gradients, and faster effective rise times. Improvements, such as narrower pulse widths, smaller erase bands, and straighter transitions for given media properties are possible if materials with high magnetic moment are used for the poles. In addition, increased over-write (OVW) on magnetic media having high coercivity can also be achieved with high moment poles. OVW, expressed in dB, is a measure of how well prior recorded information can be erased by over writing the medium with a different signal. All the above advantages become even more important at high areal densities of magnetic recording.
Efforts to find high moment alternatives to permalloy Ni80Fe20 (saturation magnetization (Bs)=1.0 Tesla (T)) and Ni45Fe55(Bs=1.6 T) typically involve alloying them with cobalt. Also, other non-magnetic elements are sometimes added to modify the properties of materials. Electrodeposition of the binary CoFe alloys, ternary CoNiFe, CoFeCu, and quaternary CoNiFeCu and CoNiFeS have been reported. High saturation magnetization films with soft magnetic properties, low magnetostriction, low stress, and high corrosion resistance are required in writing on high coercive recording media. However, the plated films need to be smooth and lump-free (free of defects). Although there are many techniques available to achieve high saturation moment at the pole tips, these techniques are relatively expensive and difficult to control. The electrochemical process needs to be easy to control while maintaining the required magnetic, corrosion, and mechanical properties.
The present invention provides a solution to these and other problems and offers other advantages over the prior art.
The present invention relates to magnetic writer poles used in magnetic data storage systems.
One embodiment of the present invention is directed to a magnetic head having a non-magnetic writer gap layer and a pair of magnetic poles separated by the writer gap layer. At least one of the poles includes a layer composed of a CoNiFe alloy that has a saturation magnetic moment greater than 2.1 T.
In one embodiment of the above-described magnetic head, the CoNiFe alloy has a saturation magnetic moment of about 2.1-2.3 T.
In another embodiment of the above-described magnetic head, the pole also has a second layer of CoNiFe alloy having a saturation magnetic moment greater than 1.8 T. The second layer is disposed adjacent the first layer opposite the writer gap layer.
Another embodiment of the present invention is directed to a method of forming a magnetic head. Pursuant to the method a substantially non-magnetic writer gap layer is formed. A pair of magnetic poles is formed, one on each side of the writer gap layer. At least one of the poles includes a layer comprising a CoNiFe alloy that has a saturation magnetic moment greater than 2.1 T.
In one embodiment of the above method, the CoNiFe alloy has a saturation magnetic moment of about 2.2 T.
In another embodiment of the above method, the pole also has a second layer of CoNiFe alloy having a saturation magnetic moment greater than 1.8 T. The second layer is formed adjacent the first layer opposite the writer gap layer.
These and various other features as well as advantages which characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.